My invention relates to a means and process for chlorination of swimming pools using elemental chlorine, cyanuric acid, and sodium hypochlorite.
I became involved in the conception, development and commercialization of the process and equipment for chlorinating swimming pools using a combination of gaseous chlorine or sodium hypochlorite and a compound selected from the group consisting of cyanuric acid, ammelide, and their salts. (For convenience in the following specification, I will usually use the expression "cyanuric acid" rather than also listing the other members of the group.)
The cyanuric acid and chlorine combine to prevent rapid hydrolysis of the chlorine by sunlight thus requiring less chlorine for swimming pool treatment. Free chlorine in an equilibrium is liberated from the combination as needed to sanitize the pool water. This method was developed and commercialization started in the 1959-1961 period and became known as the Poolchlor System. U.S. Pat. No. 2,988,471, assigned to Food Machinery Corporation, was granted June 13, 1961, and was entitled "Stabilization of Active Chlorine Containing Solutions" and concerned the use of cyanuric acid in treating swimming pools.
When chlorine (Cl.sub.2) is injected in pool water, one atom of chlorine with a valence of plus one combines with the cyanuric acid and the other chlorine atom with a valence of minus one forms hydrochloric acid. This hydrochloric acid needs to be neutralized to maintain the pH in the desired range of 7.2 to 8.2. The pool makeup water may contain some alkalinity to help in this neutralization. Some alkalyzer, such as sodium carbonate, frequently has to be added to help neutralize the hydrochloric acid.
The object of my invention includes devising a means and process using a combination of chlorine gas and sodium hypochlorite solution, at different times, to recharge the cyanuric acid when pool water becomes depleted with respect to Cl.sup.+. When chlorine gas is used, some hydrochloric acid is formed which takes care of any excess alkalinity introduced by the makeup water. When no acid is required, sodium hypochlorite (which has a neutral effect) is added to add the Cl.sup.+ to the cyanuric acid in the pool water. By the proper use of chlorine gas and sodium hypochlorite no additional alkalizer need be added to the pool water, which in the original Poolchlor System causes the problem of the precipitation of calcium carbonate from the pool water. The use of sodium hypochlorite solution according to my means and process lends itself to automatic injection as described in the attached description which is a part of this invention. It is a further objective of my invention to devise a semi-automatic means and process in adding chlorine to pool water (treated by cyanuric acid) so that service personnel need perform pool service less frequently, i.e., biweekly instead of weekly.
Another objective of my invention is to devise economical, reliable equipment to periodically add sodium hypochlorite to the inlet side of a swimming pool recirculating pump. More specifically, it is an objective to devise valve and timing means powered by a battery, especially a small battery or energizer such as a "C" battery size, to control when a vessel containing sodium hypochlorite is connected to the suction side of a pool recirculating pump.
My invention will be best understood, together with additional advantages and objectives thereof, when read with reference to the drawings.